Why dose my defogger only flows cold air? Why is the AC can not be turn off?

 

Defrost setting removes moisture in the air = AC compressor needs to be running.
Just because the AC is on, doesn't mean it will blow cold air. You might just need to adjust the temp.

 

Its covered in the manual:

A/C (Air Conditioning): This button turns the
air conditioning compressor off or on under most
conditions. The light on the A/C button comes on
when the compressor is operating. The air conditioning
does not operate at temperatures below approximately
35
F to 40
F (2
C to 4
C). The air conditioning
cools and dehumidifies the air coming into the vehicle.
The air conditioning cannot be turned off in defrost,
as it helps to remove moisture from the vehicle. It also
helps to keep the windows clear.
The air conditioning may be forced

 

Wow... a rather obnoxious feature, GM. 45 degress tonight returning from dealership where car has been for over a week getting repair work done. Raining, nasty, horrible Vette weather, and the AC is blowing cold air but I have to have it on to prevent fogging. It's a small cabin -- driven cars for years with great working defrosters and larger cabins... this would make a LOT more sense in a large-cabin car.

 

I put mine on manual, above 80* and only on the feet/bottom and then press the AC and it will blink then turn off..

 

Most cars do this today.

 

Even though the DEFROST turns the AC Compressor on, you can still turn the temperature **** from cold to HOT and have any temperature that you want blowing out of the defroster vent.

If you are able to increase the HVAC air temp normaly, you should be able to raise or lower the temp of the deforst output.

If you can NOT control the temp, read the DTCs and see if you have temp door actuator error DTC

READING YOUR Engine Diagnostic Codes



The Diagnostic Display Mode is entered with the following procedure:

1) Turn on the ignition but don't start the engine. NOTE! You can read the DTCs with the engine running and or driving down the road but it can distract you. BE careful! Some DTCs clear themselves when you turn the ignition OFF!

2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold OPTIONS
4) While holding OPTIONS, press FUEL four times within a 10-second period.


Initially, on-board diagnostics go into an Automatic Mode which shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.
There are two kinds of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current C code indicates a malfunction is present and active in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes.
More likely it's an indication of an intermittent malfunction.
Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.
Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except English/Metric (E/M). Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press and hold the RESET button To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles.
Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5. You can GOOGLE the DTC and also find information on it.




Here is very good site that explains the DTCs:


http://www.corvette-web-central.com/C5DTCcode.html


http://www.obd-codes.com/trouble_cod...d-ii-codes.php



Make sure to include the H or C suffix!!